sidestream

Sidestream is a term used across various technical fields to describe a secondary flow that diverges from a main channel, line, or process. The sidestream is usually diverted for separate treatment, analysis, or processing and may be returned to the main stream or handled independently.

In wastewater treatment, sidestreams refer to portions of liquid or slurry that are diverted from the primary flow for dedicated treatment. These streams are often subjected to specialized processes that operate at higher concentrations, temperatures, or loading rates, such as sidestream anaerobic digestion or sidestream nutrient removal. Treating sidestreams can improve overall treatment efficiency, enable energy recovery, and reduce chemical demand. Challenges include managing higher pollutant concentrations, odor control, equipment corrosion, and capital costs associated with additional infrastructure.

In smoking and environmental health discourse, sidestream smoke denotes the portion of tobacco smoke emitted from the burning end of a cigarette, pipe, or cigarette-like product, as opposed to mainstream smoke inhaled by the smoker. Sidestream smoke contributes to secondhand smoke exposure and typically has a different chemical composition and concentration profile, often with higher relative amounts of certain toxicants due to lower combustion temperatures. Public health research and policy discussions examine the risks and exposure patterns associated with sidestream smoke.

Other uses of the term arise in engineering and process monitoring, where sidestream sampling or measurement taps withdraw a sample or stream from a larger process for quality control, analytics, or control purposes. The concept of sidestream generally emphasizes a secondary, separate pathway that can be managed independently of the main flow.